[Docs] Update dashboard docs for interactive managed dashboard popover (#198226)

## Summary

Added a Duplicate dashboards page for the general duplicating process
and then mentioned the new popover for duplicating managed dashboards.
Linked to this page from other relevant mentions.

docs/user/dashboard/create-dashboards.asciidoc

@@ -83,6 +83,7 @@ image::https://images.contentstack.io/v3/assets/bltefdd0b53724fa2ce/bltf75cdb828
 [[save-dashboards]]
 . **Save** the dashboard. You can then leave the **Edit** mode and *Switch to view mode*. 
 
+NOTE: Managed dashboards can't be edited directly, but you can <<duplicate-dashboards,duplicate>> them and edit these duplicates.
 
 [[reset-the-dashboard]]
 === Reset dashboard changes
@@ -155,6 +156,24 @@ Copy panels from one dashboard to another dashboard.
 [role="screenshot"]
 image:https://images.contentstack.io/v3/assets/bltefdd0b53724fa2ce/blt64206db263cf5514/66f49286833cffb09bebd18d/copy-to-dashboard-8.15.0.gif[Copy a panel to another dashboard, width 30%]
 
+[[duplicate-dashboards]]
+== Duplicate dashboards
+
+. Open the dashboard you want to duplicate.
+
+. In *View* mode, click *Duplicate* in the toolbar.
+
+. In the *Duplicate dashboard* window, enter a title and optional description and tags.
+
+. Click *Save*.
+
+You will be redirected to the duplicated dashboard.
+
+To duplicate a managed dashboard, follow the instructions above or click the *Managed* badge in the toolbar. Then click *Duplicate* in the dialogue that appears. 
+
+[role="screenshot"]
+image::images/managed-dashboard-popover-8.16.0.png[Managed badge dialog with Duplicate button, width=40%]
+
 == Import dashboards
 
 You can import dashboards from the **Saved Objects** page under **Stack Management**. Refer to <<managing-saved-objects,Manage saved objects>>.

docs/user/dashboard/dashboard.asciidoc

@@ -17,7 +17,7 @@ There are several <<panels-editors,panel editors>> in {kib} that let you create
 // add link to sharing section
 At any time, you can <<share-the-dashboard,share a dashboard>> you've created with your team, in {kib} or outside.
 
-Some dashboards are created and managed by the system, and are identified as `managed` in your list of of dashboards. This generally happens when you set up an integration to add data. You can't edit managed dashboards directly, but you can duplicate them and edit these duplicates.
+Some dashboards are created and managed by the system, and are identified as `managed` in your list of dashboards. This generally happens when you set up an integration to add data. You can't edit managed dashboards directly, but you can <<duplicate-dashboards,duplicate>> them and edit these duplicates.
 
 --
 

docs/user/dashboard/drilldowns.asciidoc

@@ -1,6 +1,6 @@
 [role="xpack"]
 [[drilldowns]]
-=== Drilldowns
+=== Add drilldowns
 
 Panels have built-in interactive capabilities that apply filters to the dashboard data. For example, when you drag a time range or click a pie slice, a filter for the time range or pie slice is applied. Drilldowns let you customize the interactive behavior while keeping the context of the interaction.